In-line strainer with tension control mechanisms for use on high tensile wire

ABSTRACT

An in-line strainer for placement within a span of wire fence to apply tension thereto is provided. The in-line strainer includes a reel having a hollow central hub for receiving a torque limiting mechanism. The torque limiting mechanism includes a central axle and a spring mechanism. As the axle is manually rotated, the reel is also rotated through its engagement with the torque limiting mechanism until a target tension on the wire is reached. Once the target tension has been reached, the torque limiting mechanism disengages, allowing the axle to “slip” relative to the reel, preventing further rotation of the reel and, consequently, further tensioning of the wire. In addition, the in-line strainer includes a failure mechanism which ensures that, when the load threshold on the fence is exceeded, the in-line strainer will automatically release tension on the wire wound thereon in a predictable and safe manner.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is related to wire fencing and, more particularly,to a device for controlling maximum tension during installation of hightensile wire fence and for providing a predictable release mechanismwhen tension overload occurs.

2. Description of the Related Art

When installing high tensile wire fence, such as for livestock, it isnecessary to place a specified amount of tension on the wire. Typically,this tension is applied after the wire has been strung around a fenceperimeter by installing an in-line strainer at spaced locations alongspans of fencing. A representative conventional in-line strainerinstalled on a wire extending between two fence posts is shown inFIG. 1. The use of in-line strainers to tension wire fencing is wellknown in the art.

A commonly recommended pre-load for high tensile fences is 250 lb oftension. To set the pre-tension of the wire, existing in-line strainermethods rely on a compression or tension indicator spring which isinstalled on the fence wire before it is tensioned. The tensionindicator spring generally includes indicators, such as notches, thatare initially obscured by the spring and thereafter become visible asthe wire is tensioned and the spring is compressed. In one such spring,the appearance of a first notch indicates 150 lb of tension, and theappearance of the second notch indicates 300 lb of tension. However,“reading” the spring is often a matter of interpretation, leaving theinstaller uncertain as to whether the correct pre-tension level has beenreached.

Regardless of whether the tension indicator spring functions effectivelyand is “read” correctly, current in-line strainers can be tightenedbeyond the recommended tension to the point of catastrophic failure ineither the wire or the strainer. The manner in which the failure occursafter maximum load has been exceeded is unpredictable and random, whichcan result in injury to the person installing the fence or othercollateral damage, as significantly tensioned parts of the strainerand/or the fence wire are suddenly released to effectively act ashigh-speed projectiles. Similarly, even if the fence wire is properlytensioned, over-tensioning can occur during use, such as by alivestock-imposed load on the fence, which again results inunpredictable and random forms of wire and/or tensioning mechanismfailure.

Accordingly, a need exists for an in-line strainer that can be used toeffectively tension wire fencing to the recommended pre-load whilepreventing over-tensioning during installation. A need also exists foran in-line strainer that, when subjected to excess loads on the fencewire following installation, breaks in a predictable, repeatable andsafe manner.

SUMMARY OF THE INVENTION

In view of the foregoing, the present invention is directed to anin-line strainer for placement within a span of wire fence to applytension thereto. The in-line strainer includes a reel, rotatablysupported by a body, for spooling up the fence wire during tensioning.The reel is provided with external teeth that engage a pawl which issupported by the body and held by spring tension against the reel toprevent the reel from unwinding. The center of the reel has an innerwall that defines a hollow center portion for receiving a torquelimiting mechanism. The torque limiting mechanism includes a centralaxle and a spring mechanism and, when engaged with the reel, transfersrotational force from the axle to the reel. Specifically, as the axle ismanually rotated, the reel is also rotated through its engagement withthe torque limiting mechanism until the target tension on the wire isreached. Once the target tension has been reached, the torque limitingmechanism disengages, allowing the axle to “slip” relative to the reel,preventing further rotation of the reel and, consequently, furthertensioning of the wire.

In one preferred embodiment, the torque limiting mechanism includes atleast one detent operative with the spring mechanism that is receivedwithin at least one notch in the inner wall of the reel when the torquelimiting mechanism is engaged. When the force needed to turn the reelbecomes greater than the resistance created by the detent's positionwithin the notch, the axle rotates relative to the reel and the detentmoves out of the notch to disengage the torque limiting mechanism.Preferably, the “slipping” movement of the torque limiting mechanismrelative to the reel produces audible or tactile feedback to theinstaller that the disengagement has occurred.

The present invention further includes a failure mechanism which ensuresthat, when the load threshold on the fence is exceeded, the in-linestrainer will break or otherwise release in a predictable and safemanner. In one preferred embodiment, the failure mechanism includes aline of weakness such as a notch in the side of the pawl. When the wiretension is too great, the pawl will fold or fracture along the line ofweakness, allowing the reel to unwind which releases the tension on thewire.

Accordingly, it is an object of the present invention to provide anin-line strainer that overcomes the difficulties encountered with priorart devices when trying to achieve an accurate pre-load on high tensilefences, the present invention including a reel with a torque limitingmechanism that prevents the wire from being tensioned beyond the desiredpre-tension level.

Another object of the present invention is to provide an in-linestrainer in accordance with the preceding object in which the reel has ahollow central hub and the torque limiting mechanism includes a centralaxle with a spring mechanism fitted within the center of the reel thatrotates with the reel when the torque limiting mechanism is engaged andthat slips relative to the reel when the torque limiting mechanism isdisengaged.

A further object of the present invention is to provide an in-linestrainer in accordance with the preceding objects in which the reel hasexternal teeth that are engaged by a pawl to keep the reel fromunwinding, the pawl having a failure mechanism that ensures that thein-line strainer will break in a predictable and safe manner whentension on the wire exceeds maximum safe load.

Yet another object of the present invention is to provide an in-linestrainer in accordance with the preceding objects in which the failuremechanism includes a notch in the side of the pawl that forms a line ofweakness along which the pawl will fold or fracture when tension on thewire exceeds maximum safe load.

A still further object of the present invention is to provide an in-linestrainer in accordance with the preceding objects in which the torquelimiting mechanism includes a notch formed in an inner wall of thereel's hollow central hub, and a detent operative with the springmechanism that fits within the notch when the mechanism is engaged andmoves out of the notch to disengage the mechanism.

Yet a further object of the present invention is to provide an in-linestrainer in accordance with the preceding objects in which the movementof the detent out of the notch produces audible or tactile feedback tothe fence installer of the disengagement.

Another object of the present invention is to provide an in-linestrainer in accordance with the preceding objects that is not complex instructure and which can be manufactured at low cost but yet effectivelyprevents wire fencing from being tensioned beyond a desired pre-tensionduring installation and, during use, provides for safe and predictablefailure when maximum safe load on the fence wire is exceeded.

These together with other objects and advantages which will becomesubsequently apparent reside in the details of construction andoperation as more fully hereinafter described and claimed, referencebeing had to the accompanying drawings forming a part hereof, whereinlike numerals refer to like parts throughout.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a conventional in-line strainer installed on a wireextending between two fence posts.

FIG. 2 is a perspective view of an assembled in-line strainer inaccordance with a first embodiment of the present invention.

FIG. 3 is an exploded view of the in-line strainer shown in FIG. 2.

FIG. 4 is a perspective view of one of the straps shown in FIG. 3, asviewed from the outer side with respect to the assembly shown in FIG. 2.

FIG. 4A is a top view of the strap shown in FIG. 4.

FIG. 4B is a side view of the strap shown in FIG. 4, as viewed from theinner side with respect to the assembly shown in FIG. 2.

FIG. 4C is a cross sectional view taken along line A-A of FIG. 4B.

FIG. 4D is an enlarged view of the area denoted Detail D in FIG. 4C.

FIG. 4E is a cross sectional view taken along line B-B of FIG. 4B.

FIG. 4F is an end view of the strap shown in FIGS. 4 and 4B.

FIG. 5 is a perspective view of the reel shown in FIG. 3, as viewed fromthe axle-insertion side, designated herein as the right side and asshown in FIGS. 2 and 3.

FIG. 5A is a perspective view of the reel shown in FIG. 5 from the leftside.

FIG. 5B is another perspective view of the reel shown in FIG. 5 from theright side and rotated 90°.

FIG. 5C is a view of the right side of the reel shown in FIG. 5.

FIG. 5D is a view of the left side of the reel shown in

FIG. 5.

FIG. 5E is an end view of the reel shown in FIG. 5.

FIG. 5F is a cross sectional view taken along line A-A of FIG. 5E.

FIG. 5G is an end view of the reel shown in FIG. 5.

FIG. 5H is a cross sectional view taken along line C-C of FIG. 5G.

FIG. 6 is a perspective view of the axle shown in FIG. 3, as viewed fromthe axle-tightening side, designated herein as the right side and asshown in FIGS. 2 and 3.

FIG. 6A is a perspective view of the axle shown in FIG. 6 from the leftside.

FIG. 6B is a top view of the axle shown in FIG. 6.

FIG. 6C is a side view of the axle shown in FIG. 6.

FIG. 6D is an end view from the left side of the axle shown in FIG. 6C.

FIG. 6E is an end view from the right side of the axle shown in FIG. 6C.

FIG. 7 is a perspective view of the spring mechanism shown in FIG. 3.

FIG. 7A is a side view of the spring mechanism shown in FIG. 7.

FIG. 7B is a top view of the spring mechanism shown in FIG. 7.

FIG. 8 is a perspective view of the detent embodied as a dowel pin asshown in FIG. 3.

FIG. 8A is a side view of the dowel pin shown in FIG. 8.

FIG. 8B is an enlarged view of the area denoted Detail B in FIG. 8A.

FIG. 8C is an end view of the dowel pin shown in FIG. 8A.

FIG. 9 is a perspective view of the pawl as shown in FIG. 3.

FIG. 9A is a top view of the pawl shown in FIG. 9.

FIG. 9B is a side view of the pawl shown in FIG. 9A.

FIG. 9C is an end view of the pawl shown in FIG. 9A.

FIG. 10 is a perspective view of the pawl spring as shown in FIG. 3.

FIG. 10A is a side view of the pawl spring shown in FIG. 10.

FIG. 10B is an end view from the left side of the pawl spring shown inFIG. 10A.

FIG. 10G is a view of the pawl spring shown in FIG. 10B as rotated 90°on a horizontal axis.

FIG. 10D is a top view of the pawl spring shown in FIG. 10A.

FIG. 11 illustrates the basic components of a torque limiting mechanismhaving an axle, a spring mechanism and a detent, in accordance with thepresent invention.

FIG. 12 illustrates a modified version of the torque limiting mechanismshown in FIG. 11, having an axle, spring mechanism and two detents.

FIG. 13 illustrates a conventional tool used to turn the reel of anin-line strainer to tension a fence wire.

FIG. 14 shows a detent sequentially engaged in a notch, beginning todisengage, and then disengaged from the notch in accordance with theoperation of a torque limiting mechanism of the present invention.

FIG. 15 is a perspective view of an assembled in-line strainer inaccordance with a second embodiment of the present invention.

FIG. 16 is an exploded view of the in-line strainer shown in FIG. 15.

FIG. 17 is an assembled view of a third embodiment of a torque limitingmechanism in accordance with the present invention.

FIG. 18 is an exploded view of the third embodiment components shown inFIG. 17.

FIG. 19 is a side view of the torsion spring installed in the reel ofthe embodiment shown in FIG. 17.

FIG. 20 is an assembled view of a fourth embodiment of a torque limitingmechanism in accordance with the present invention.

FIG. 21 is an exploded view of the fourth embodiment components shown inFIG. 20.

FIG. 22 is a side view of the key and spring installed in the reel ofthe embodiment shown in FIG. 20.

FIG. 23 is an assembled view of a fifth embodiment of a torque limitingmechanism in accordance with the present invention.

FIG. 24 is an exploded view of the fifth embodiment components shown inFIG. 23.

FIG. 25 is a side view of the clutch limiter installed in the reel ofthe embodiment shown in FIG. 23.

FIG. 26 is an assembled view of a sixth embodiment of a torque limitingmechanism in accordance with the present invention.

FIG. 27 is an exploded view of the sixth embodiment components shown inFIG. 26.

FIG. 28 is a side view of the clutch limiter installed in the reel ofthe embodiment shown in FIG. 26.

FIG. 29 is an assembled view of a seventh embodiment of a torquelimiting mechanism in accordance with the present invention.

FIG. 30 is an exploded view of the seventh embodiment components shownin FIG. 29.

FIG. 31 is a side view of the clutch limiter installed in the reel ofthe embodiment shown in FIG. 29.

FIG. 32 is a side view of a notched pawl failure mechanism in accordancewith the present invention.

FIG. 33 depicts the notched pawl failure mechanism of FIG. 2 uponfailure.

FIG. 34 is an isolated perspective view of the broken pawl shown in FIG.33.

FIG. 35A is a perspective view of an alternate embodiment of a notchedpawl in accordance with the present invention.

FIG. 35B is a planar view of the pawl shown in FIG. 35A.

FIG. 35C is a side view of the pawl shown in FIG. 35A.

FIG. 36 is a perspective view of a further embodiment of a notched pawlhalf in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In describing a preferred embodiment of the invention illustrated in thedrawings, specific terminology will be resorted to for the sake ofclarity. However, the invention is not intended to be limited to thespecific terms so selected, and it is to be understood that eachspecific term includes all technical equivalents which operate in asimilar manner to accomplish a similar purpose.

As shown by a first embodiment in FIGS. 2 and 3, and in more detail on acomponent by component basis in FIGS. 4-10C, the present invention isdirected to an in-line strainer, generally designated by referencenumeral 10, for placement within a span of wire fence to apply tensionthereto. The in-line strainer 10 includes a body or strap generallydesignated by reference numeral 12, a reel 14, a torque limitingmechanism generally designated by reference numeral 16, and a reelholding mechanism generally designated by reference numeral 18.

The strap 12 can be a unified member or, as shown in FIGS. 3, 4 and4A-4F, may be comprised of two separate strap members 12 a and 12 b thatare connected to one another when the strainer is assembled as shown inFIG. 2. The two strap members are identical which facilitates ease ofmanufacture, with each strap member having a body 20 with an axlemounting aperture 22, a pawl mounting aperture 24, a pair of pawl springmounting loops 26, and a fence wire mounting aperture 28, as will bedescribed more fully hereinafter. The body 20 has a curved portion 30that enables the respective fence wire mounting apertures 28 of twostrap members, as assembled, to be in abutment with one another whilethe axle mounting apertures 22 and pawl mounting apertures 24 of suchstrap members are spaced apart to provide room therebetween for the reel14 and reel holding mechanism 18, respectively.

As is conventional, the reel 14 includes a plurality of external teeth32 separated from one another by hollows 34 and is rotatably supportedby the pair of strap members 12. When the strainer is installed along awire span, the wire is cut to create two ends (see FIG. 1). The firstwire end 33 is secured to the strap by passing the wire through thefence wire mounting apertures 28 and crimping the wire upon itself atcrimp 31 (see FIG. 13). The second wire end 35 is inserted through awire hole 36, preferably on one side of the reel hub 15 (see FIGS. 3 and5B), and bent to secure the wire to the reel prior to tensioning of thewire. Such installation steps are well known in the art.

According to the first embodiment of the present invention, the hub 15of the reel 14 has a hollow central portion generally designated byreference numeral 40, defined by an inner wall 42 having a plurality ofnotches 44 spaced around the inner wall 42 and separated from oneanother by high points 46. Several views of the reel 14 are provided inFIGS. 5 and 5A-5H. As best shown in FIGS. 5A, 5B and 5F, the notches 44do not extend all the way through the reel so as not to interfere withsecuring the wire end 35 inside the reel hub 15. Other configurations ofthe hollow central portion 40 are also possible, some of which are shownand discussed hereinafter.

The torque limiting mechanism 16 includes a central axle generallydesignated by reference numeral 50, a spring mechanism generallydesignated by reference numeral 52, and a detent generally designated byreference numeral 54. While only one detent is illustrated in FIG. 3,there are in fact two detents in this embodiment, with one detent beingpositioned on either end of the spring mechanism.

According to the first embodiment, the axle 50 has a longitudinallyextending body 56 that extends at least partly through the centralportion 40 of the reel. The body 56 has a central channel 58 that passesthrough the body 56 transversely to the longitudinal axis of the axle 50as shown in FIGS. 6 and 6A-6E. The ends of the axle 50, in longitudinalalignment with and on either side of the body 56, include toolengagement heads 60, 62 for operative engagement with a correspondinglydesigned tool used to rotate the axle 50 as will be discussedhereinafter. One such tool being used to rotate a conventional reel isshown in FIG. 13.

The spring mechanism 52, shown in FIGS. 7, 7A and 7B, is received withinthe central channel 58. According to the first preferred embodiment, thespring mechanism 52 is a polyurethane member, although other flexiblematerials that meet the release force requirements for achieving propertension on the wire could also be used. Other alternative constructionsfor the spring mechanism 52 include a compression spring, torsionspring, Belleville springs, or other comparable spring mechanisms.

The detents 54 can also be variously configured as will be discussedhereinafter. In the first embodiment shown in FIGS. 2, 3, 8, 8A and 8B,the detents are dowel pins positioned adjacent each of the ends of thepolyurethane member spring mechanism 52. The detents 54 preferably havechamfered ends 64 to facilitate insertion of the axle 50, springmechanism 52 and detents 54 into the hollow central portion 40 of thereel 15 during assembly, but chamfering the ends is not necessary.

When the torque limiting mechanism 16 is inserted into the hollow centerportion 40 of the reel 14 upon assembly of the in-line strainer 10 asshown in FIG. 2, the detents 54 are configured to engage with thenotches 44 formed in the inner wall 42 of the reel, under thecompression force provided by the spring mechanism 52. When rotationalforce is exerted on the axle tool engagement heads 60, 62, the axlerotates and, through the engagement of the detents 54 and the reelnotches 44, the reel also rotates. The stiffness of the springmechanism, the materials from which the reel inner wall and the detentsare made, and the shape of the detents determine the resistance of thetorque limiting mechanism 16 to disengagement. These parameters may beadjusted during manufacture to obtain the desired threshold at which thetorque limiting mechanism will begin to “slip” relative to the reel.

While being rotated by the axle, the reel is prevented from unwinding bythe reel holding mechanism 18. The reel holding mechanism 18 includes apawl generally designated by reference numeral 70 and shown in detail inFIGS. 9 and 9A-9C, and a pawl spring generally designated by referencenumeral 72 and shown in detail in FIGS. 10 and 10A-10D.

The pawl 70 has an axle 74 coupled to a flap 76 that has at least onereel-engagement arm 78 that is received within one of the reel hollows34 between the external teeth 32. Preferably, the pawl 70 has tworeel-engagement arms 78, each of which engage one side of the reel. Thepawl axle 74 is pivotally mounted to the strap members 12 by insertingthe axle ends 80 through the pawl mounting apertures 24. As the reel 14is rotated, the flap 76, rotating on the pawl axle 74, moves thereel-engagement arm 78 from one reel hollow 34 to an adjoining hollow insequence. The sides 29 (see FIG. 5C) of the reel teeth 32 are sloped tofacilitate this movement of the arm 78 as it slides along the side 29 ofthe tooth 32 before dropping into the next adjoining hollow 34 as thereel rotates. Once the arm drops into a hollow, the reel is preventedfrom unwinding by the pawl 70.

To ensure that the pawl 70 moves into and stays engaged within the reelhollows 34, the pawl spring 72 exerts a spring force on the pawl flap 76to force the arm 78 against the reel 14. The ends 82 of the pawl spring72 are secured in the pawl spring mounting loops 26 formed on the inwardfacing sides of the strap 12, while the middle portion 84 of the pawlspring 72 presses against the pawl flap 76.

In operation, the torque limiting mechanism 16, when mounted within thereel 14 in the assembled strainer, transfers rotational force from theaxle 50 to the reel 14. The fence installer tightens the reel by turningthe axle 50 using an appropriate tool as applied to the tool engagementheads 60, 62 on the axle. As the axle is manually rotated, the reel isalso rotated through its engagement with the torque limiting mechanism16 until the target tension on the wire is reached. This target tensionis determined by the specific construction of the in-line strainer,taking into account the materials used, the depth of the notches, theshape of the detent, etc. Once the target tension on the wire has beenreached, the force needed to turn the reel becomes greater than theresistance created by the position of the detents 54 within the opposednotches 44. At this point, further rotation of the axle 50 causes eachdetent to move out of its notch into the next adjoining notch, thuseffectively “disengaging” the torque limiting mechanism. If the operatorcontinues to try to tension the wire, the detents of the torque limitingmechanism will continue to ratchet from one notch to the next, allowingthe axle to “slip” relative to the reel so that further tensioning ofthe wire is prevented.

Preferably, the movement of the detents out of the notches producesaudible or tactile feedback to the installer of the disengagement. Suchfeedback informs the installer that the in-line strainer is operatingproperly and that the desired tension has indeed been achieved.

While the above-described first embodiment includes two detents 54, itshould be noted that in its most basic form a single detent may besatisfactory. As illustrated in FIG. 11, the torque limiting mechanismaccording to the present invention generally designated by referencenumeral 100 includes a central axle 150, a spring mechanism generallydesignated by reference numeral 152, and a single detent generallydesignated by reference numeral 154. Alternatively, a slightly morecomplex torque limiting mechanism, generally designated by referencenumeral 110, can include an axle 151, a spring mechanism 153 and a pairof detents 154, 155 as shown in FIG. 12; the first embodiment shown inFIGS. 2 and 3 is an example of such a paired detent configuration.

The torque limiting mechanism can also be made with three or moredetents through appropriate placement of a second and/or third springmechanism, or more, with the detents being spaced around the perimeterof the axle. It would even be possible to have as many detents as thereare notches in the inner wall of the reel. The number of detents that ispreferred depends upon the materials from which the reel, the detentsand the spring mechanism are made; the shape and size of the detents;and the load to be placed on the wire being tensioned. However, thepresent invention only requires a single notch and a single detent towork effectively.

The central channel 159 in the axle 151 can pass all the way through theaxle, as shown in FIG. 12 and according to the first embodiment, or thecentral channel 158 can extend only partly through the axle 150 as shownin FIG. 11. In either case, the spring mechanism 152, 153 is receivedwithin the central channel 158, 159, with a detent 154 being positionedon one end of the spring mechanism 152 in the case of one detent (FIG.11), or with the detents 154, 155 positioned on each end of the springmechanism 153 in the case of two detents (FIG. 12).

The stages by which a detent 154 moves out of a correspondingly shapednotch 144 to disengage the torque limiting mechanism are illustrated inFIG. 14. As shown, in the initial stage, identified as “1” in FIG. 14,the detent has full or nearly full face contact with the notch; completefull face contact may not occur due to manufacturing variation. As theforce needed to turn the reel increase, the detent 154 begins to sliprelative to the notch as shown in the stage marked “2”. Finally, whenthe force needed to turn the reel becomes greater than the resistancecreated by the position of the detent 154 within the opposed notch 144,the detent moves out of the notch 144 as shown in the stage marked “3”.At this point, further rotation of the axle 150 does not result infurther rotation of the reel.

Assembled and exploded views of a second embodiment of an in-linestrainer according to the present invention, generally designated byreference numeral 200, are shown in FIGS. 15 and 16, respectively. As inthe first embodiment, the in-line strainer 200 includes a body or strapgenerally designated by reference numeral 212, a reel 214, a torquelimiting mechanism generally designated by reference numeral 216, and areel holding mechanism generally designated by reference numeral 218. Asthese components operate in a manner like that already described inconnection with the first embodiment, description of these componentswill not be repeated except to identify differences with respect to thefirst embodiment. Also, elements of the same basic type as used in eachof the embodiments are designated in the particular embodiments thatfollow with the same two-digit number as in the first embodiment butpreceded by a “2” for the second embodiment, a “3” for the thirdembodiment, etc.

In the second embodiment, the side straps 212 a, 212 b have a differentconfiguration from those shown in the first embodiment, but theiroperation remains the same. In the second embodiment the straps aredesigned to be snapped together, but alternatively may be weldedtogether as in the first embodiment. The straps may also be screwed orriveted to one another, or connected using other fastening devices aswould be understood by persons of ordinary skill in the art.

In addition, the side straps 212 a, 212 b include an integrated springelement 272 that forms part of the reel holding mechanism 218 along withthe pawl 270. For ease of manufacture, both side straps 212 a, 212 b areof identical construction. Therefore, the spring element 272 that endsup on the bottom of the in-line strainer when two of the side straps areconnected to one another is extraneous in terms of function, while theupper spring element 272 applies spring tension to the pawl 270. Ratherthan dowel pins, the detents in the second embodiment are embodied askeys 254 having a flat lower surface 255 that abuts with the springmechanism 252 and a rounded upper surface 257 that engages with thenotches 244 in the inner wall 242 of the reel 214. The inner wall 242 ofthe reel 214 only has two notches 244, rather than the multiplicity ofnotches spaced all around the inner wall 242 of the reel 214, as in thefirst embodiment. Hence, in the second embodiment, the axle 250 can turnnearly 180 degrees upon disengagement of the detents 254 with thenotches 244. As this degree of movement upon disengagement can bedisruptive or startling to the installer, the multiplicity of spacednotches around the reel as provided in the first embodiment, whichlimits release movement to a small increment, is preferred.

As shown, the torque limiting mechanism in both the first and secondembodiments have similar features, including a polyurethane member andkeys or dowels that are held between the urethane member and the notchesin the reel to provide engagement between the axle and the reel. Variousother configurations of the torque limiting mechanism are also providedaccording to the present invention as will now be described.

FIGS. 17-19 illustrate a third embodiment of the torque limitingmechanism according to the present invention, which is generallydesignated by reference numeral 300. As in the first and secondembodiments, the torque limiting mechanism 300 includes an axle 350 thatis received within the hollow center 340 of the reel 314. Rather thanthe urethane member and keys/dowels, the third embodiment relies upon atorsion spring 352. A first end 353 of the torsion spring 352 is lockedto the axle 350, such as by a longitudinal slot 351. The second end ofthe torsion spring includes a detent 354, which engages in the notch 344in the inner wall 342 of the reel 314. As with the dowel pins and keysof the first and second embodiments, the detent 354 of the torsionspring 352 pops out of the notch 344 when the target torque limit on theaxle is exceeded, allowing the axle 350 to turn relative to the reel314.

A fourth embodiment of the torque limiting mechanism according to thepresent invention is illustrated in FIGS. 20-22 and generally designatedby reference numeral 400. The fourth embodiment is similar to the secondembodiment, except that only a single key 454 is used as wasrepresentatively shown in FIG. 11.

A fifth embodiment of the torque limiting mechanism in accordance withthe present invention is illustrated in FIGS. 23-25 and generallydesignated by reference numeral 500. A compression spring 552 issandwiched between two pressure plates 553 and secured within the hollowcentral portion 540 of the reel by nuts 550. The pressure plates 553 areprovided with peripheral detents 554 that engage corresponding notches544 in the reel inner wall 542. A shoulder screw 557 is inserted throughaligned apertures 559 in the pressure plates 553 and twisted to compressthe spring 552. Upon sufficient compression of the spring, the detents554 on the pressure plates will disengage from the reel notches 544 in amanner similar to the previous embodiments.

A sixth embodiment of the torque limiting mechanism according to thepresent invention is illustrated in FIGS. 26-28 and generally designatedby reference numeral 600. In this embodiment, the axle is formed by twonuts 650 which serve as the tool engagement heads on either side of thereel 614. A urethane spring 652 is inserted into the bore 651 of each ofthe nuts 650 and then tightened to the desired degree with a respectiveshoulder screw 657. The nuts 650 are rotated to turn the reel 614 andtension the wire until the springs 652 exceed the frictional forcespreventing rotation and allow “slip” within the bores.

A seventh embodiment of the torque limiting mechanism in accordance withthe present invention is illustrated in FIGS. 29-31 and generallydesignated by reference numeral 700. This embodiment operates similarlyto the sixth embodiment, except that the axle does not go all the waythrough the reel 714. Belleville springs 752 are compressed by shoulderscrew 757 until interference surfaces 754 acting as detents “slip”relative to an engagement surface 759 in the center of the reel 714.

Other embodiments are also contemplated that would operate in a similarmanner to limit the amount of tension that can be applied to a strand ofwire. In each case, an axle is operative with the reel of the in-linestrainer to rotate with the reel up to a desired torque and to then bereleased from the reel to rotate independently therefrom so that furtherrotation of the reel, and subsequent tensioning of the wire, isprevented.

The in-line strainer of the present invention further includes anintegral release or failure mechanism which causes the strainer torelease when a predetermined load on the fence wire is exceeded. Thefailure mechanism thus ensures that, when the load threshold on thefence wire is exceeded, the in-line strainer will break or otherwiserelease in a predictable and safe manner to release the tension on thewire. Since the in-line strainer according to the present invention isdesigned to prevent over-tensioning of the wire during initialinstallation, the failure mechanism is provided with an eye towardcontrolling tension on the fence and in-line strainer during actual use.

As shown in FIGS. 3 and 9 and previously described in connection withthe first embodiment, the pawl 70 has an axle 74, a flap 76 and at leastone reel-engagement arm 78. As shown in FIG. 9B, one side 86 of the flapis provided with a stress point such as a notch 88. The pawl may bepositioned so that the notched side 86 faces upwardly as in FIG. 32. Thenotched side 86 may alternatively be positioned to face downwardly asshown in FIGS. 3 and 9. The notch 88 creates a line of weakness alongwhich the pawl 70 will fold or fracture when the wire tension is toogreat. Upon folding or fracturing of the pawl 70 along the line ofweakness formed by the notch 88, as shown in FIGS. 33 and 34, the reel14 is free to unwind which releases the tension on the wire.

An alternate embodiment of the pawl is shown in FIGS. 35A-35C andgenerally designated by reference numeral 170. In this embodiment, theouter edge 178 of the flap 176 serves as the reel-engagement arm. Afurther embodiment generally designated by reference numeral 270, shownin FIG. 36, includes a reel-engagement pin 278 positioned opposite andgenerally parallel with the pawl axle 274.

The release or failure mechanism according to the present inventioncould also be embodied so that, rather than breaking, the pawl or anassociated component automatically “kicks out” of engagement with thereel in response to a tension overload on the wire.

The foregoing descriptions and drawings should be considered asillustrative only of the principles of the invention. The invention maybe configured in a variety of shapes and sizes and is not limited by thedimensions of the preferred embodiment. Numerous applications of thepresent invention will readily occur to those skilled in the art.Therefore, it is not desired to limit the invention to the specificexamples disclosed or the exact construction and operation shown anddescribed. Rather, all suitable modifications and equivalents may beresorted to, falling within the scope of the invention.

1. An in-line strainer for tensioning wire fencing comprising: a bodyrotatably supporting a reel onto which fence wire is wound to tensionsaid fence wire, said reel having a plurality of alternating externalteeth and notches; a pawl pivotally mounted to said body for engagingsaid notches on said reel to prevent said reel from unwinding as saidfence wire is tensioned; and a torque limiting mechanism engaged withsaid reel and configured to rotate said reel up to a threshold wiretension, said torque limiting mechanism disengaging from said reel whensaid threshold wire tension is reached so that further winding rotationof said reel is prevented.
 2. The in-line strainer as set forth in claim1, wherein said reel has a hollow center portion and said torquelimiting mechanism includes an axle and a spring mechanism receivedwithin said hollow center portion, rotation of said axle concurrentlyrotating said reel through engagement of said spring mechanism with saidreel center portion until rotational force required to rotate said axleexceeds a resistance provided by said engagement.
 3. The in-linestrainer as set forth in claim 2, wherein said torque limiting mechanismfurther includes a detent positioned between said spring mechanism andan inner wall of said hollow center portion, said inner wall includingat least one notch into which said detent is received to provide saidresistance while said torque limiting mechanism is engaged.
 4. Thein-line strainer as set forth in claim 2, wherein said axle includes athrough-passing channel, said spring mechanism being received withinsaid channel, said torque limiting mechanism further including a pair ofdetents positioned on either side of said spring mechanism and againstan inner wall of said hollow center portion, said inner wall includingat least two opposed notches into which said detents are received toprovide said resistance while said torque limiting mechanism is engaged.5. The in-line strainer as set forth in claim 4, wherein said inner wallincludes a regular alternating pattern of notches and high pointsregularly spaced around said inner wall, said detents moving from onepair of notches to a next sequential pair of notches upon disengagementof said torque limiting mechanism, said movement creating at least oneof tactile and audible feedback to a fence installer tensioning saidfence wire each time the detents move to a subsequent pair of notches.6. The in-line strainer as set forth in claim 1, wherein said in-linestrainer further includes a failure mechanism that breaks in apredictable and repeatable manner when said threshold wire tension isexceeded.
 7. The in-line strainer as set forth in claim 6, wherein saidfailure mechanism includes a line of weakness in said pawl, said line ofweakness being substantially parallel with an axis of rotation of saidreel.
 8. The in-line strainer as set forth in claim 7, wherein said lineof weakness is formed by a notch in an upper surface or a lower surfaceof said pawl.
 9. In an in-line strainer for tensioning wire fencing,said in-line strainer having a body rotatably supporting a reel ontowhich fence wire is wound to tension said fence wire, a reel having aplurality of alternating external teeth and notches, and a pawlpivotally mounted to said body for engaging said notches on said reel toprevent said reel from unwinding as said fence wire is tensioned, theimprovement comprising: said reel having a hollow center portion; and atorque limiting mechanism engaged within said hollow center portion andconfigured so that rotation of said torque limiting mechanismconcurrently rotates said reel up to a threshold wire tension, saidtorque limiting mechanism disengaging from said reel to rotateseparately therefrom when said threshold wire tension is reached so thatfurther rotation of said reel is prevented.
 10. The in-line strainerimprovement as set forth in claim 9, wherein said torque limitingmechanism includes an axle and a spring mechanism received within saidhollow center portion, rotation of said axle concurrently rotating saidreel through the engagement of said spring mechanism with an inner wallof said center portion until rotational force required to rotate saidaxle exceeds a resistance provided by said engagement.
 11. The in-linestrainer improvement as set forth in claim 10, wherein said torquelimiting mechanism further includes a detent positioned between saidspring mechanism and said inner wall, said inner wall including at leastone notch into which said detent is received to provide said resistancewhile said torque limiting mechanism is engaged.
 12. The in-linestrainer improvement as set forth in claim 10, wherein said axleincludes a through-passing channel, said spring mechanism being receivedwithin said channel, said torque limiting mechanism further including apair of detents positioned on either side of said spring mechanism andagainst said inner wall, said inner wall including at least two opposednotches into which said detents are received to provide said resistancewhile said torque limiting mechanism is engaged.
 13. The in-linestrainer improvement as set forth in claim 12, wherein said inner wallincludes a regular alternating pattern of notches and high pointsregularly spaced around said inner wall, said detents moving from onepair of notches to a next sequential pair of notches upon disengagementof said torque limiting mechanism, said movement creating at least oneof tactile and audible feedback to a fence installer tensioning saidfence wire each time the detents move to a subsequent pair of notches.14. The in-line strainer improvement as set forth in claim 9, whereinsaid in-line strainer further includes a failure mechanism that breaksin a predictable and repeatable manner when said threshold wire tensionis exceeded.
 15. The in-line strainer as set forth in claim 14, whereinsaid failure mechanism includes a line of weakness in said pawl, saidline of weakness being substantially parallel with an axis of rotationof said reel.
 16. The in-line strainer as set forth in claim 15, whereinsaid line of weakness is formed by a notch in an upper surface or alower surface of said pawl.
 17. An in-line strainer for controllingtension on wire fencing comprising: a body rotatably supporting a reelonto which fence wire is wound to tension said fence wire, said reelhaving a plurality of alternating external teeth and notches; a pawlpivotally mounted to said body for engaging said notches on said reel toprevent said reel from unwinding as said fence wire is tensioned; and afailure mechanism associated with said pawl that releases tension on thefence wire in a predictable and repeatable manner when a predeterminedthreshold wire tension is exceeded.
 18. The in-line strainer as setforth in claim 17, wherein said failure mechanism includes a line ofweakness in said pawl along which the pawl breaks when the predeterminedthreshold wire tension is exceeded, said line of weakness beingsubstantially parallel with an axis of rotation of said reel.
 19. Thein-line strainer as set forth in claim 18, wherein said line of weaknessis formed by a notch in an upper surface or a lower surface of saidpawl.
 20. The in-line strainer as set forth in claim 17, furthercomprising a torque limiting mechanism engaged with said reel andconfigured to rotate said reel up to said threshold wire tension, saidtorque limiting mechanism disengaging from said reel when said thresholdwire tension is reached so that further winding rotation of said reel isprevented.